1. Field of the Invention
The present invention relates to lightning suppression attenuator. More particularly, the present invention relates to devices for reducing the magnitude of current of a lightning current wavefront as it moves along a power line from a power strike. More particularly, the present invention relates to devices for protecting electrical systems and critical load systems of facilities that are connected to a power line subject to lightning strikes.
2. Description of Related Art
Lightning conceivably may have provided humankind with a first source of fire, but lightning has otherwise been a destructive force throughout human history. Strategies and apparatus for reducing the likelihood of damage by lightning are fairly old, including, for instance, lightning rods that have been use for approximately 200 years. While the use of such rods and other precautionary steps and safety devices reduce the damage and injury that would otherwise result from lightning today, it remains an enormously dangerous natural phenomenon that claims hundreds of lives worldwide every year and destroys a substantial amount of property. Somewhat paradoxically, advances in other areas of technology have increased, rather than diminished, the damaged caused by lightning. This is because relatively low voltage and current levels can damage integrated circuits and other modern electronic components, with the result that many electronic devices are more susceptible to lightning damage today than ever before. Many devices to which microprocessors technology has been added are more susceptible to lightning damage as a result of such improvements. Additionally, lightning is capable of inducing substantial currents not only in electrical circuits directly struck by it but also in circuits located within the magnetic field induced by a nearby lightning strikes, giving each strike enormous destructive potential.
One of the most common areas of lightning strikes are large telecommunications and camera towers that extend upwardly from the earth. Typically, such towers include an electronic device at the top which serves to transmit or receive information. Since lightning will follow a path of least resistance on its way to the earth, the towers are very attractive to lightning. It is well known that lightning is particularly attracted to areas of positive ions and is repelled by areas of negative ions. Since the electronic devices at the top of towers often operate on AC power, an attractive source of positive ions is generated at the top of the tower.
A major problem associated with lightning strikes is the propagation of the lightning current wavefront along power lines. Quite commonly, power lines exist on elevated towers that are especially subject to lightning strikes. In other circumstances, the power lines can be positioned so that they are subject to ground transference of the wavefront of current from a lightning strike to the earth or an adjacent building. The lightning wavefront through the power line can travel to various instruments, devices and appliances that are connected to the power supply. If the lightning wavefront is of sufficient magnitude, then any lightning suppression devices connected to the power supply will be insufficient in preventing damage to the equipment connected to the power supply. This can result in damage that is expensive and requires time-consuming repair.
In the past, various U.S. patents have issued relating to lightning suppression attenuators. For example, U.S. Pat. No. 5,844,766, issued on Dec. 1, 1998 to L. Miglioli, describes a lightning suppression system for tower mounted antenna systems. This lightning strikes includes a directional coupler, a quarter-wavelength stub, a first cylindrical capacitor, a second cylindrical capacitor and a lightning suppression circuit. The lightning suppression circuit suppresses high voltage direct current and low frequency signals such as those produced by near lightning strikes. The lightning suppression circuit includes a gas discharge tube, an inductor element, a varistor, a resistor element and a zener diode. The gas discharge tube and the inductor element are connected to a second cylindrical capacitor. The varistor and the resistor element are connected to an inductor element. The zener diode and the amplifier are connected to the resistor element.
U.S. Pat. No. 5,167,537, issued on Dec. 1, 1992 to Johnescu et al., describes a high density MLV contact assembly capable of low working voltages and high energy handling capacity, including lightning suppression. This assembly employs a multi-layered varistor as the transient suppression device.
It is an object of the present invention to provide a lightning suppression attenuator that effectively prevents lightning strikes from affecting equipment connected to a power supply.
It is another object of the present invention to provide a lightning suppression attenuator that effectively minimizes the magnitude of a lightning current as it moves along a power line.
It is a further object of the present invention to provide a lightning suppression attenuator which minimizes the damaging effects of lightning.
It is a further object of the present invention to provide a lightning suppression attenuator which is easy to install, relatively inexpensive and easy to manufacture.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.
The present invention is a lightning suppression system comprising an enclosure having an interior volume, a first coil positioned within the interior volume of the enclosure, a second coil positioned within the interior volume of the enclosure, and a power supply connected to the leads of the first and second coils. A third coil can be also positioned within the interior volume of the enclosure. The power supply is also connected to the leads of the third coil.
Where two coils are used in the enclosure, the power supply is a single phase power supply. Where three coils are positioned on the interior of the enclosure, the power supply is a three phrase power supply.
A grounding rod is connected by a conductive line to the enclosure. The grounding rod includes a central shaft, and a plurality of vanes extending radially outwardly from the central shaft. The central shaft and the plurality of vanes are formed of a conductive material. A conductive band extends around the interior volume of the enclosure. The conductive line is connected to this conductive band. A conductive grit fills a portion of the enclosure. In the preferred embodiment of the present invention, the conductive grit is steel shot. A rigid foam material can be affixed within the enclosure around the conductive grit and over the coils.
Each of the first and second coils has a central void with turns of wire extending around the central void. In the preferred embodiment of the present invention, the wire is 600 volt black superflex copper wire. The coil has greater than 30 turns of wire around the central void. Each of the coils has leads which extend outwardly of the enclosure for connection to the power supply.